DESCRIPTION: (Applicant's abstract verbatim) The cost of dental care in the United States was $45.8 billion in 1995. Replacement of dental restorations accounts for 75 percent of all operative work, and secondary caries at the margins of restorations is the most frequently identified reason for replacement (Kidd, 1996). Thus, dental patients can realize considerable cost savings and improved oral health care if the lifetime of defective restorations can be extended through the use of tooth preservation therapies. The overall objective of this study is to test the hypothesis that application to marginal crevices of a sealing resin that releases chlorhexidine and/or fluoride (when the pH decreases to below 6.0) can extend the service life of defective amalgam and composite restorations and enhance remineralization of demineralized adjacent enamel. We propose to test the following hypotheses- (1) polymer microspheres loaded with chlorhexidine diacetate alone, a dispersed mixture of either CaF2 or ZnF2 and chlorhexidine diacetate, or one of these fluoride agents alone will exhibit an onset of ion release when the solution pH decreases below 6.0 and will terminate ion release when the pH increases above 6.0; (2) the controlled-release microspheres when loaded in a resin matrix (bis GMA/TEGDMA/HEMA), will exhibit an initial release rate when the solution pH decreases below 6.0 and will reduce its release rate when the solution pH increases above 6.0; (3) Test the hypothesis that microbial accumulation (plaque) and site specific levels of S. mutans on tooth enamel adjacent to defective amalgam or composite restorations are significantly better predictors of secondary caries than the width of the marginal crevice and; whole mouth levels of S. mutans; and (4) a crevice-sealing resin containing a dispersed mixture of chlorhexidine and fluoride microspheres will more effectively inhibit demineralization and enhance remineralization of enamel adjacent to composite restorations than resins containing only one of these two therapeutic agents. Clinically relevant aspects of this project include: (1) use of a monoclonal antibody test for site specific analyses of S. mutans on selected approximal tooth surfaces with amalgam or composite restorations; (2) use of a dispersed mixture of polymer microspheres that will release an antibacterial agent (chlorhexidine) simultaneous with a remineralizing agent (fluoride) to prevent secondary caries in situ; and (3) analysis of extracted restored teeth to determine the best of four predictors for secondary caries (plaque levels-at the margins of restorations, whole mouth concentrations of S. mutans, site specific levels of S. mutans at the margins of amalgam and composite restorations, and the width of marginal crevices adjacent to amalgam and composite restorations).